There are some perfectly logical reasons I never suggest anyone
slather some sealant on pneumatics in a player piano:

1. The cloth is cotton.  When cotton cloth is 50 to 120 years old,
it has oxidized; just like when you dog-ear an old book and that
triangle of paper breaks right off instead of creasing, so cloth
oxidizes.  Both cotton and wool get crispy and break when folded.
This is also why we replace felt bushings and other felts throughout
the player systems.  So coating the old cloth with sealant is a waste
of time in many cases.

2. The extra thickness slows down the action.  When pneumatics are
close together you can't get a thin coat of something down in the
space, so you end up with gobs that dry and then you have what we
call "hinge bound" but it is actually caused by sealant.

3. Someone has to go to extra work to get all that sealant gunk off
before they can recover your pneumatics when you finally do the
required restoration

Recovering pneumatics is such a minor job for one experienced in
such that it is only a few hundred dollars to have done professionally.
Now, often in older pianos, valves are also needed making, making an
investment of about $2000 also required, but in a Kimball Electramatic
valves are rarely needed and recovering those pneumatics is between
$500 and $1000.   Now regluing or gasketing those valve units back
into place may add a couple hundred dollars as well, but you should
count your blessings if you need to rebuild one of these.  Compare
the Kimball to a full size 1920 player which takes $6500 or more to
completely restore, and that's just player system.

Doing this right means you have a functional piano for another 50 or
more years.  Glopping up with sealant means you have an unknown period
of a year to 3 or 4 years before you are forced to do it right anyway.

Your Kimball will also need the gearbox opened, cleaned and repacked
with a replacement brass version of that compound fiber gear inside.
Be careful of the leaf switches found around the spoolbox as they can
bend; they control the reroll/replay/shutoff system.

Doug L. Bullock
http://thepianoworld.com/